1. Field
The present invention relates to a method for transmitting a signal, particularly to methods and apparatuses for transmitting and receiving a high-order modulated signal.
2. Description of Related Art
One of the most representative methods of digital modulation methods is quadrature amplitude modulation (QAM), in which a digital signal constituted with bit strings is modulated by sorting the bit string into groups of predetermined bits and modifying the amplitude and phase of a carrier signal.
Digital modulation methods use a constellation that indicates a distance between a digital signal and a neighboring signal. The QAM method using the constellation is advantageous for reducing an average power consumption while maintaining the conventional modulation symbol error probability.
That is, the QAM method is the representative high-order modulation method used for improvement of transmission speed, and an M-ary (=2m) QAM symbol can transfer m bits of information. Accordingly, if a hexadecimal QAM is used, each modulation symbol can transfer 4 bits of gray-mapped different information. Moreover, since each modulation symbol has to be at an intersecting point of a square lattice, the I-axis and Q-axis coordinates of the modulation symbol for the hexadecimal QAM are fixed numbers of ±d or ±3d, whereas d is a real number of 0 or greater.